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Additive manufacturing, otherwise known as three-dimensional (3D) printing, has revolutionized the construction industries in numerous ways over the past several years. Recent interest has been on advancing the practice of additive manufacturing of concrete (AMoC).
Why Concrete?
Throughout the world, concrete has remained the most used building material as a result of its affordability, durability, moldability and fire resistance. While concrete is an umbrella term that encompasses materials of various compositions, all concrete materials typically contain some type of filler in the form of sand, gravel or other granulate. Furthermore, the filler of concrete must be bound together by a matrix that arises as a result of some type of exothermal hydration reaction between the cementitious material and water.
Although the use of concrete material provides obvious advantages in construction, its production is often extremely arduous for those involved. For example, the burning of granulated blast furnace slag (GGBFS) to produce hydraulic cement is a particularly laborious process to complete that also plays a significant role in contributing much of the worldwide carbon dioxide (CO2) emissions. Another energy-intensive aspect of concrete production involves the molding of cement and placement of these structures, which can lead to a number of health effects to these construction workers.
Current AMoC Technology
While AMoC remains in its infancy, many researchers and private construction companies are have remained committed to developing and improving different AMoC methods. One of the most commonly used AMoC technology is Countour Crafting, which is a layered fabrication technology that utilizes both robotic arms and extrusion nozzles to construct the walls of buildings. This 6-axis robot is controlled by an XYZ gantry system that manages its extrusion, rotation and trowel deflection movements. To ensure the creation of smooth concrete surfaces, the Contour Crafting utilizes two distinct trowels that act as two solid planar surfaces during concrete manufacturing.
Researchers at Loughborough University in Leicestershire, England have developed the D-shape method, which utilizes a powder deposition process that closely resembles the action of 3D inkjet printing. As compared to the completely wet process performed by Contour Crafting, the D-shape method instead is a completely dry manufacturing process. Furthermore, the D-shape method provides construction workers with significantly greater precision capabilities as compared to Contour Crafting as a result of its smaller resolution of deposition during printing. It is important to note that both the D-shape method and Contour Crafting have proven their ability to create large construction structural components.
Challenges
Some of the most critical technical challenges that the developers of AMoC continue to face involves the need to standardize material formulations, as well as improve the interface bonding that exists between the 3D printing concrete layers and other materials. The lack of AMoC standardization as a technology also leads to potential legal issues in which current legislative policies are limited in their ability to regulate AMoC practices within the construction industry. In regard to the technical aspects of the AMoC process, researchers are still working to improve the capabilities of AMoC methods to produce precise, uniform and functional concrete products.
Conclusion
Many construction professionals will agree that AMoC has the potential to resolve many of the traditional issues that construction workers face in the manufacturing, molding and placement of concrete materials. As the technology behind additive manufacturing continues to advance and be applied within the construction industry, its inevitable role in improving occupational health and construction efficiency, as well as reducing CO2 emissions and its effects will follow.
References and Further Reading
- . Additive manufacturing of concrete in construction: potentials and challenges of 3D concrete printing - Bos, F., Wolfs, R., Ahmed, Z., & Salet, T. Virtual and Physical Prototyping 3; 209-225. (2017). DOI: 10.1080/17452759.2016.1209867.
- Additive manufacturing technology and its implementation in construction as an eco-innovative solution - Ghaffar, S. H., Corker, J., & Fan, M. Automation in Construction 92; 1-11. (2018) DOI: 10.1016/j.autocon.2018.05.005.
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